1. Field of the Invention
This invention relates to new aqueous bleaching compositions containing alkali metal hypochlorites, alkali metal hydroxides and a ternary inhibitor system and to the use of the ternary mixture as an incrustation and yellowing inhibitor for the production of aqueous bleaching compositions.
2. Discussion of Relative Art
Whereas powder-form or liquid heavy-duty detergents which only develop their cleaning performance at relatively high temperatures are used in many European countries for washing heavily soiled textiles, consumers in the USA and Spain, for example, preferred cold washing where a liquid bleach, preferably based on hypochlorite, is added in addition to a detergent in order to remove particularly difficult stains.
Numerous liquid bleaching compositions are known from the prior art. Thus, EP-A 0 274 885 (ICI), for example, recommends the use of mixtures of linear and branched amine oxides for the production of viscous hypochlorite bleaches. According to the teaching of EP-A 0 145 084 (Unilever), mixtures of amine oxides with soaps, sarcosinates, taurides or sugar esters may also be used for this purpose. The use of amine oxides with soap or sarcosinate and other anionic surfactants, for example alkyl sulfates, alkyl ether sulfates, secondary alkane sulfonates or alkyl benzenesulfonates, as thickening component for hypochlorite solutions is known from EP-A 0 137 551 and EP-A 0 447 261 (Unilever). EP-A 0 156 438 reports on the use of alkylaryl sulfonates as thickeners in aqueous bleaching compositions which contain certain stilbene dyes as optical brighteners. ES-A 8801389 (Henkel Iberica) relates to bleaching compositions based on aqueous hypochlorite solutions which predominantly contain alkyl ether sulfates and, in addition, small amounts of amine oxides as surfactant component. In addition, aqueous bleaching compositions containing sodium hypochlorite and anionic surfactants are known from EP-A1 0 447 261. However, the hypochlorite concentration of these compositions is between 0.1 and 8% by weight and preferably between 0.5 and 5% by weight of active chlorine. In German patent DE-C1 4 333 100, applicants propose aqueous bleaching and cleaning compositions based on hypochlorites, fatty alcohol ether sulfates, amine oxides and amine oxide phosphonic acids.
International patent applications WO 94/10272, WO 95/03383, WO 95/08610 and WO 95/08611 (Procter & Gamble) relate to hypochlorite-containing bleaching compositions containing short-chain anionic surfactants such as, for example, octyl sulfate. European patent application EP-A 0 688 857 (Procter & Gamble) describes hypochlorite-containing bleaching compositions containing periodates and carbonates for adjusting the pH value. European patent application EP-A 0 688 345 (Procter & Gamble) relates to hypochlorite-based bleaching compositions containing small quantities of silicates and/or carbonates, polycarboxylates and radical scavengers. An alkaline hypochlorite-based bleaching composition containing carbonates and silicates for stabilizing perfume oils is also proposed in European patent application EP-A 0 622 451 (Procter & Gamble).
Bleaching compositions of the type mentioned above are expected to satisfy stringent consumer requirements. They have to be laundry-compatible, i.e. the treatment with the basically aggressive chemical hypochlorite is expected to remove stains without affecting the fabric. Since skin contact with the bleaching compositions cannot be ruled out, the compositions are also expected to be as dermatologically safe as possible. In cases where hard water is used for the washing process, there is the problem of lime deposits on the fibers and hence the danger of fabric incrustation, especially in the event of prolonged exposure to the composition. Another problem is that hypochlorite solutions also attack metals and the traces of metals dissolved in this way can be deposited on the textile fibers during the washing process which is ultimately reflected in yellowing of the fabric.
Accordingly, the complex problem addressed by the present invention was to provide storage-stable, non-clouding aqueous bleaching compositions which, at one and the same time, would be chlorine-stable, laundry-compatible and dermatologically safe, would have a sufficiently high viscosity and, for a high stain removing power, would reliably prevent the deposition of lime and metal traces on the fabrics.